The query refinement approach is motivated by the idea that while it may be difficult for a user to formulate a good query when she does not know the collection well (e.g., in exploratory search), it is easy to judge the relevance of returned documents. The iterative query reformulation process can be effective in tracking a user's evolving information need [1]}, [2]}.
The Rocchio algorithm [3]} is a classic query refinement method where the feedback data is used to re-weight query terms in a vector space.
